The fine droplets in the spray mist generated during spraying of a pesticide formulation can travel with the wind, hence exposing human, wildlife, and the environment to pesticide residues that may have health and environmental effects and may cause property damage.
Various methods have been proposed in an attempt to reduce the amount of drifting of fine droplets during spraying of an aqueous pesticide solution. One method is to modify the nozzle design so as to allow bigger spray droplets when the liquid passes through of the nozzle. Another method is to use a drift control chemical agent. Various drift control agents are known, including polymers and surfactants. One useful polymer class is a high molecular weight water soluble polysaccharides such as derivatives of guar gum and xanthan gum. It has been generally accepted that the mechanism of drift control by polymers is that these polymers increase the elongational (or extensional) or kinematic (or intrinsic) viscosity of the diluted aqueous solution to, for example above 6 dl/g. The increased viscosity usually results in increased droplet size and reduced fines. Over the years, researchers have found that the optimum spray pattern has a droplet size distribution in the mist between 150-400 μm. Guar gum derivatives are efficient drift control agents. They can reduce the fine droplets dramatically even at a very low concentration such as ˜<0.06 wt.
Cellulose is a polysaccharide built up from 1,4-anhydroglucose units. The cellulose molecules in native cellulose are insoluble in water. To make cellulose soluble, it has to be modified into a cellulose derivative, such as hydroxyethyl cellulose (HEC), ethyl hydroxyethyl cellulose (EHEC), hydroxylpropyl cellulose (HPC), hydroxybutyl methylcellulose (HBMC), hydroxypropyl methylcellulose (HPMC), methyl ethyl hydroxyethyl cellulose (MEHEC), and hydrophobically modified ethyl hydroxyethyl cellulose (HMEHEC).
The use of some cellulose derivatives as drift control agents has been known. While there is a preference for cellulosic derivatives over guar and xanthan gum due to their abundance and renewable property, these cellulose derivatives have marginal drift control property.